Pressure-proportioning device



Nov. 8, 1960 A. P. ROBERTS 2,959,225

PRESSURE-PROPORTIONING DEVICE Filed Feb. 10, 1958 2 Sheets-Sheet '1Fla-'4 Alan P. Roberts Inventor 5W 4. Attorney Nov. 8, 1960 A. P.ROBERTS PRESSURE-PROPORTIONING DEVICE 2 Sheets-Sheet 2 Filed Feb. 10,1958 OION o Inventor Alan P. Roberts By% M Attorney the borehole wall.

PRESSURE-PROPORTIONING DEVICE Alan P. Roberts, Tulsa, Okla., assignor,by mesne assignments, to Jersey Production Research Company Filed Feb.10, 1958, Ser. No. 714,140 9 Claims. 61. 166-147) This invention relatesto a pressure-proportioning device. It relates more particularly to apressure-proportioning device for distributing the mud column loadbetween well packers when at least two packers are spaced longitudinallyin a borehole between the outer wall of a tubular member disposed withinthe borehole and the borehole wall for reducing hydrostatic pressure ina part of the borehole.

In the drilling operations in which a borehole is drilled in the earthin order to locate formations or reservoirs from which oil or gas may beobtained, it is quite frequently advantageous and desirable to isolatethe area in which the bit is drilling from the remainder of the an nularspace between the drill pipe and the walls of the well bore. It is knownthat by reducing the hydrostatic pressure on the face of the formationbeing drilledpdrill- States Patent 6 ing efliciency will be greatlyincreased. A recent technique developed which takes advantage of thisfactor for" increasing drilling efliciency is the so-called air or gasdrilling method. In this method a drill bit is suspended at the lowerend of a string of drill pipe which is supported from the surface of theearth and is rotated from the surface in a conventional manner. Adrilling fluid is' forced downward through the drill string through thedrill bit and back up to the surface through the annulus between thedrill pipe and the walls of the borehole. The drilling fluid servesprimarily to carry the rock cuttings from the drill bit to the surfaceand to cool the drill bit. It is readily seen that the use of air orgas, replacing drilling mud or water as the cleaning medium, givesrather substantial improvement in penetration rates and bit life.

However, it should be noted that the use of air or gas as a cleaningmedium is not without problems. Perhaps the greatest single obstacle inthe way'of using air or gas as a cleaning medium is the water or otherfluid encountered in the various formations penetrated by the borehole.The ingress of water into the borehole and down the same to the bit maybe a serious problem. The water wets the cuttings and causes balling ofthe cuttings and if the volume of water is suflicien-t, the balling willplug the hole or stick the drill pipe, thus causing the abandonment ofthe air or gas drilling operation. One method of overcoming thisobstacle is the use of a drill string suspended within a casing. The airis circulated down through the drill string and back to the surfacethrough the annulus between the drill string and the casing. A packer isset between the casing and the wall of the borehole and a drilling mudof a proper density is then used to fill the annulus between the casingand It is thus seen that this permits a pressure to be kept on the wateror other fluid-producing formations which the well bore has penetrated.Quite frequently it has been found that one packer will not sustain thegreat weight of the mud column. Therefore, in such cases one or moreadditional packers must be set.

' The use of two or more packers is, of course, beneficial in that thecolumn of mud can-be more easilysustained.

rai'lgement,

. upwardly.

2959,23 Patented Nov. 8, 1950 The pressure-proportioning device uses theprinciple of using difierential areas exposed to the pressure of the mudcolumn above a top packer and the pressure in the space between thepackers. A preferred embodiment of the pressure-proportioning deviceincludes a piston with a circumferential recess intermediate its endsand a housing for receiving the piston in a sealingly and slidablerelationship. The area of the top of the piston which is subjected tothe downward force of the pressure of the mud column in the annulusbetween the casing and the borehole wall above the top packer is reducedto a de- H sired percentage of the area of the bottom of the pistonwhich is subjected to the upward force of the pressure of the fluid inthe annular cell between the two packers. It is thus seen that if theratio R between the pressure in the annular cell between the packers tothe pressure in the annulus above the packers, is equal to the ratio R:of the effective area of the top of the piston to the area of the bottomend of the piston, there is no movement of the piston. If the ratio Rdecreases below R ..the piston will move downwardly; and conversely ifthe ratio R is greater than the ratio R the piston will move When thetwo ratios are again equal, the piston will assume a neutral position.If the ratio of the pressure in the annular cell between the packers andthe pressure in the annulus above the packers is below the ratio of theareas of the ends of the piston, the piston moves downward, thus openinga conduit means which permits fluid to flow from the annulus above thepackers to the annular cell between the packers. When the ratio of thepressure in the annular cell and the pressure in the annulus above thepacker reaches the desired value, the piston is returned to its neutralposition thereby closing the conduit means. If the pressure in theannular cell between the packers becomes too high, the piston movesupward thus opening a conduit establishing fluid communication betweenthe annular cell between the packers and the space below the packers.The pressure in the annular cell is reduced to the desired proportion ofthe pressure of the mud column in the annulus above the top packer atwhich time the piston returns to its normal or neutral position, thusclosing the passageway means.

Various objects and a complete understanding of the invention willbecome apparent from the following detailed description taken inconjunction with the accompanied drawing in which:

Fig. 1 is a schematic diagram illustrating the proportioning device whenused with two packers which are spaced longitudinally in a boreholebetween the outer wall of a tubular member and the borehole well; i

Fig. 2 is an enlarged and more detailed view of the proportioning deviceillustrated in Fig. 1 showing the piston of the device in aneutralposition;

- Fig. 3 is a partial fragmentary sectional view taken along the lineIIIIlI of Fig. 2; Fig. 4 is a fragmentary cross section takensubstantially at IVIV of Fig. 2;

Fig. 5 is similar to Fig. 2 and shows a piston in'its lowermostposition; and, g

Fig. 6 is similar to Fig. 2 and shows a piston in its uppermost positionand a modification of the po'rt ar- Referring to the drawing there isillustrated the best mode contemplated for carrying out the invention.Reference numeral 12 refers to the wall of a borehole drilled through anunderground formation. Tubular cylinder 14 is suspended within theborehole and includes an upper section 16, sub 20 which is rigidlyattached to the upper section as shown at '18, and a lower section 22rigidly attached to the sub as shown at 24. 7 An "upper packer 26 and alower packer 28 are supported from the tubular cylinder 14 in alongitudinally spaced relationship. These packers may be anyconventional type and may be expandable by either'inflatable ormechanical means. The packers are shown in their expanded position andseparate the annulus between the tubular cylinder 14 and the wall of theborehole into three compartments which for convenience will be referredto as annulus 30 which is that space above upper packer 26 and betweenthe outer wall of the tubular support and the wall of the borehole, anannular cell '32 which is that space between the packers and between theouter wall of the tubular cylinder 14 and the wall of the borehole, andannular space 34 below packer '28 and between the wall of the boreholeand the outer wall of the tubular support.

Sub 20 also serves as the valve body and has defined therein main valvecylindrical chamber 36 which has its axis preferably in substantiallythe same direction as the axis of the tubular cylinder 14. A reducedpiston cylindrical chamber 38 is also provided in sub 20 and on the sameaxis as the axis of cylinder 36 and longitudinally abuts cylindricalchamber 36. A piston 40*is slidably mounted in cylindrical chamber 36with the longitudinal dimension of the piston being less than the"longitudinal dimension of the cylindrical chamber36.

.iP iston 40 has a circumferential recess 42 intermediate of its ends.The piston is urged upwardly by a resilient fmember such as spring 44disposed at the lower end of cylindrical chamber 36 and below the lowerend of piston 40. It is preferred that one end of spring 44 f isattached to sub 20 at 53 and the other end to piston "40fat 51. Anarea-proportioning rod 46 is rigidly atf tached to or made an integralpart of the top portion of piston 40. Rod 46 is slidably fitted withinpiston cylinder 38 and is'insertable therein in a sealing relationship.Seals such as O-ring seals 48 may be used to assure a seal. Pistoncylinder 38 may be either air filled or It is preferred that one end ofto piston 40 at 49. When piston 40 is in a neutral'position, springs 44and 50 are preferably under neither tension nor compression. A neutralposition of piston 40 is such that recess 42 is above'ports 64'and-68andbelow i ports 56 and 60 as shown in Fig. 2. This is also the xpositionof piston 40 when there is no fluid pressure exerted upon either area 94shown in Fig. 3 or on'area 96 shown in Fig. 4. Valve body or cylindricalchamber '36 has an upper port 52 in its upper end and above the upperend of piston 40. Port 52 through conduit 54 establishes fluidcommunication between annulus 30 and the interior of chamber 36 abovepiston 40. Valve 1 chamber 36 has an upper intermediate port 56 which"through conduit means 58 establishes fluid communica- VQV tion betweenannular cell 32 and the interior'of' chamber 36. A second upperintermediate port 60 is lateral- Q ,ly and circumferentially spaced inchamber'36 from port 56. Port 60 together with conduit '62 providesfluid communication between theinterior of'valve chamber 36 and annularspace 34.

lt will be noted that when the piston is in the posifias asfl h w l .Fsf the drawing the valved 'pass'a'geWay means between annular cell-32and the '{annular space 34 is closed. When the piston i's-movedupward itis readily seen that this valved passageway is open as recess 42 is sopositioned on piston 40 as to align with ports 56 and 60 when piston 40is in its uppermost position. This is shown in Fig. 6 and in thisposition ports 64 and 68 are still covered by piston 40 and sealingelements 68, 80, and 82 sealingly engage piston 40 in fluid excludingengagement. A lower intermediate port 64 together with conduits 54 and66 establishes fluid communication between annulus 30 and the interiorof cylindrical chamber 36. A second lower intermediate port 68 isprovided for cylindrical chamber 36 and is circumferentially andlaterally spaced from port 64. A lower port 70 is provided incylindrical chamber 36 and is positioned below the lower end of piston40. A conduit 72 connects ports 68 and 70. A port 74 is provided in thelower end of cylindrical chamber 36 and is circumferentially andlaterally spaced from port 70. A conduit 76 together with a conduit 58establishes fluid communication between the annular cell 32 and theinterior of cylindrical chamber 36 below piston 40. When piston 40 is inits lowermost position, the various components are so designed thatrecess 42 is aligned with ports 64 and 68. In other words when spring 44is fully compressed, recess 42 of piston 40 is aligned with ports 64 and68. At this position, sealing elements 84 and 86 still engage piston 40in fluid excluding engagement. This is shown in Fig. 5. It is thus seenthat valved conduit means establishing fluid communication betweenannulus 30 and annular cell 32 is established through conduit 54,conduit 66, recess 42, conduit 72, the interior of cylinder 36, andconduits 76 and 58. I

Various modifications of the port arrangement of Fig. 2 may be made. Forexample, in Fig. 6 port 52A opens into the upper end of cylindricalchamber 36. Port 70A is illustrated as opening into the other endofcylindrical chamber 36.

Piston 40 may be fitted within cylindrical chamber 36 with a maximumtolerance of approximately .001 inch which is normally adequate toprevent any leakage through the valve. However, for most drilling mudsit will be preferred to use sealing means such as illustrated in Fig. 2.This includes seal 80 below ports 64 and 68, seals 82 and 83 betweenports 56 and 60 and ports 64 and 68, and seal 84 above ports 56 and 60.These seals 80, 82, 83 and 84 may be O-ring seals or other types such asV seals. Seal 86 is provided in recess 88 at port 60 and likewise a seal90 is provided in recess 92 of port 68. Seals 86 and 90 are preferablyof the V type.

As hereinbefore disclosed, the pressure-proportioning "device operateson the principle of using differential areas exposed to the mud columnpressures above the top packer and in the annular cell between thepackers to move a floating piston which opens the proper valve ports'soas to distribute the pressure. For example, if it is desired for packers26 and 28 to each support onehalf of the mud column load, that is, thepressure drop across packer 26 is to be equal to one-half the mud columnload, then the area 94 of the top of the piston exposed to the pressureabove the top packer would be one-half area. 96 of the bottom of piston40 which is exposed to the pressure of the fluid in the annular cell 32between the packers.

When the packers are initially set the hole is usually full of mud.-After the packers are set, the mud is blown 5 pressure in the annulus 30above the top packer. It is thus seen that the product of the pressureof the fluid in -the annular cell 32 times area 96 of the piston isapproxilmately twice that of the'product of the pressure of -the=--fl'uid* in annulus 30 times-the area- 94. Inthis caselthe piston willhave axial movement upward. This causes recess 42 of the piston to alignwith ports 56 and 60 of the valved cylinder. This permits fluid to flowfrom annular cell 32 to the annular space 34 as the pressure in theannular space 34 is reduced by being removed therefrom by the air orgas. When the pressure in the annular cell 32 is equal to one-half thepressure in the annulus 30, it is seen that the upward and downwardforces on the piston due to the fluid pressure in annulus 30 and annularcell 32 is equal. The resilient means such as springs 44 and 50 urgesthe piston downwardly into a neutral position thus stopping the flow offluid from annular cell 32 through the valved body to the' annularspace34. Springs 44 and 50 are preferably designed such that they are notunder tension or compression when the piston is in a neutral position.The recess 42 in piston 40 is so positioned that at this neutralposition it will be above ports 64 and 68 and below ports 56 and 60, asshown in Figure 1. It is also seen that at this point the passagewayfrom the annulus 30 to the annular cell 32 is closed. If the pressure inan-- nular cell 32 should exceed one-half the pressure in annulus 30, itis obvious that the piston 40 will be urged upwardly as the pressure ofthe fluid in annular cell 32 times the area 96 is greater than theproduct of the pressure of the fiuid in the annulus 30 times the area94. Recess 42 will'then be aligned with ports 56 and 60. Fluid isthenreleased from annular cell 32 to the annular space 34 below the bottompacker. When the pressure in annular cell 32 is reduced to one-half thepressure in annulus 30, the piston will once more be urged into itsneutral position which, as shown in Figure 1, will effectively close thepassageway means from the annular cell 32 to the annular space 34. Ifthe pressure in annular cell 32 drops below one-half the pressure inannulus 30, it is obvious that piston 40 will be urged downwardly thusaligning ports 64 and 68 with recess 42. The pressure in annular cell 32then builds up until it is equal to one-half the pressure in annulus 30at which time the piston is returned to its neutral position closing theconduit means from annulus 30 to annular cell 32. It is of courseunderstood that by varying the ratio of area 94 with respect to 96, anydesired weight distribution can be accomplished between annulus 30 andthe annular cell 32. It is also understood that additional packers andadditional pressure-proportioning devices may be utilized together forany desired pressure distribution over any desired numb-er of packers.

When the piston moves upward, spring 50 is compressed and spring 44 isunder tension; and, when the piston 40 moves downwardly, spring 44 iscompressed and spring 50 is under tension. It is thus seen that bothsprings 44 and 50 tend to urge the piston into a neutral position. It iscontemplated that the pressure required to move piston 40 from itsneutral position is approximately five pounds. This inertia of thepiston would have a negligible effect upon the proportioning of the loadto the two individual packers when compared to the total load of the mudcolumn which may be as high as 3,000 pounds per square inch for a 6,000foot hole.

There are many uses for this proportioning device. One use contemplatedis the drilling operation in which a different fluid is used as thecirculating medium for removing the cuttings from that which is in theannulus behind the casing. In such a case, the drill string is suspendedwithin the casing. The two packers support the mud column between thecasing and the borehole wall with the mud serving primarily to seal theformations or prevent flow therefrom. The packers will be used to keepthe mud load from being exerted upon the bottom of the borehole as theformation is being drilled. Air or other fluid is then circulated downthrough the drill string through the drill bit where it picks upcuttings and carries them back up to the surface through the annulusbetween the drill string and the casing. An exclaimed in US. Patent No.2,338,670 issued to Sewell.

on January 4, 1944. Other uses for this system will be obvious to thoseskilled in the art.

It is to be understood that various changes and modifications in thisinvention may be made without departing from the scope thereof.

The invention claimed is:

1. In a drill string having spaced packers thereon for sealing off theannulus between the drill string and the borehole wall, pressureproportioning device mounted in said string intermediate said packersfor controlling the pressure differential across the upper of said twovertically spaced packers which comprises a tubular body, a differentialpiston and cylinder assembly'mounted in the wall of said tubular body,said piston having opposite end portions with fluid pressure actuatablesurfaces, the fluid pressure actuated surface on the first end portionof said piston having a lesser cross-sectional area than the fluidpressure actuated surface on the opposite end portion thereof; the wallof said cylinder being provided with a first port above said first endportion, second and third laterally spaced ports at a first intermediatelevel in said cylinder wall, fourth and fifth laterally spaced ports ata second intermediate level in said cylinder wall, and a sixth port insaid cylinder wall below said opposite end portion of said piston, afirst conduit interconnecting said first port with the exterior of saidstring of drill pipe above the upper of said packers, a second conduitinter-' connecting said fourth port with said first conduit, a thirdconduit interconnecting the exterior of said assembly between saidpackers with said sixth port, a fourth conduit interconnecting saidsecond port with said third conduit, a fifth conduit interconnectingsaid fifth port with said third conduit, a sixth conduit interconnectingthe exterior of said assembly below the lower of said packers with saidthird port; a transverse passageway in said piston intermediate itslength positionable to intercommunicably connect said second and thirdports in one extreme position of said piston within said cylinder andintercommunicably connect said fourth and fifth ports when in theopposite extreme position.

2. An apparatus as defined in claim 1 including biasing means tending toposition said transverse passageway at a point intermediate its twoextreme positions.

3. An apparatus as defined in claim 1 wherein said passageway is acircumferential recess around said piston.

4. In a drill string having spaced packers thereon for sealing off theannulus between the drill string and the borehole wall, apressure-proportioning sub mounted in said string intermediate saidpackers for controlling the pressure differential across the upper ofsaid two vertically spaced packers which comprises: a first cylindricalchamber in the Wall of said sub, said first chamber being provided witha first port in the upper end thereof, second and third ports laterallyspaced at a first intermediate position along the wall of said firstchamber, fourth and fifth ports laterally spaced along the Wall of saidfirst chamber at a second intermediate position, and a sixth port nearthe lower end of said first chamber; a second chamber having a smallerdiameter than said first chamber and coaxially aligned with and openinginto said first chamber; a piston member having a first section in asealing and slidable relationship within said first chamber and a secondsection slidable within said first and second chambers and having asealing relationship with said second chamber, the first section of saidpiston having a transverse passageway intermediate its ends; firstconduit means interconnecting the exterior of said sub above said upperpacker with said first and fourth ports; second conduit meansinterconnecting the exterior of said sub between said packer with saidsecond port and said sixth port; third conduit means interconnecting theexterior of said sub below said lower packer with said third port; a

fourth conduit means interconnecting said fifth port with said sixthport; said piston and said first chamber being further characterizedsuch that said transverse passageway in said piston. is' positionable tointercommunicably' connect said second and third ports in one extremeposition of said piston within said cylinder and intercommun'ic'ablyconnect said fourth and fifth ports when in the opposite extremeposition. I I I 5. An apparatus as defined in claim 4 including biasingmeans to position said piston means within said first chamber with saidtransverse passageway at. a. point intermediate its two extremepositions.

6. An.apparatus as defined in claim 5 wherein said passageway is acircumferential recess around said piston.

7. In a drill string having spaced packers thereon for sealing oh theannulus between the drill string and the borehole wall, apressure-proportioning device mounted inv said string intermediate saidpacker for controlling the pressure dififerential across the upper ofsaid two vertically spaced packers which comprises: a tubular body, adifferential piston and cylinder assembly mounted on the wall of saidtubular body, said piston having opposite end portions with fluidpressure actuatable surfaces, the fluid pressure actuated surface on afirst end portion of said piston having a lesser cross-sectional areathan the fluid pressure actuatable surface on the opposite end portionthereof; the wall of said cylinder being provided with afirst port abovesaid first end portion, second and third laterally spaced ports at afirst intermediate level infsaid cylinder wall, fourth and fifthlaterally spaced ports at a second intermediate level in said cylinderwall, and sixth I and seventh ports laterally spaced at a lower level insaidcylinder wall below said opposite end portion of said piston;a'first conduit interconnecting-said firstportwiththe exterior of saidstring of drill pipe above the upperof said packers and with said fourthportrasecondconduit interconnecting the exterior'of said-assembly between said packers with said secondport'andsaid sixthport; a fourthconduit interconnecting said fiftlr'port witlf said seventh port; afifth conduit interconnecting thex terior of said assembly below thelower of said packer with said third port; a transverse passagewayinsaid pis ton intermediate its length positionable to intercommuni"cably connect said second and third ports in oneextreme References Citedin the file of this patent- UNITED STATES PATENTS 2,813,587 Mounce Nov.19; 1957 Bierman Mar. 31} 1953 gym Ens-4

